Components in the hot gas flow path of gas turbines often have cooling channels. Cooling effectiveness is important to minimize thermal stress on these components, and cooling efficiency is important to minimize the volume of air diverted from the compressor for cooling. Film cooling provides a film of cooling air on outer surfaces of a component via holes from internal cooling channels. Film cooling can be inefficient, because a high volume of cooling air is required. Thus, film cooling has been used selectively in combination with other techniques. Impingement cooling is a technique in which perforated baffles are spaced from a surface to create impingement jets of cooling air against the surface. Serpentine cooling channels have been provided in turbine components, including airfoils such as blades and vanes. The present invention increases effectiveness and efficiency in cooling channels.